There is no quick fix for obesity - exercise devices on TV targeting fat are a hoax, for example. Where is the first place most people lose weight? Their face, yet no one is exercising their face.

So-called natural remedies for people desiring quick obesity fixes are also a lucrative market but a new study of medical records in Hong Kong revealed 66 cases where people were suspected to have been poisoned by a 'natural' slimming therapy. In eight cases the people became severely ill, and in one case the person died.

To find out why, the researchers looked at the ingredients in the 81 slimming products that these people had taken. They found 12 different agents that fell into five categories: undeclared weight-loss drugs; drug analogues (unlicensed chemical derivatives of licensed drugs); banned drugs; drugs used for an inappropriate indication; and thyroid hormones.

Dr. Magdalene Tang, who works at the Toxicology Reference Laboratory at the Princess Margaret Hospital in Hong Kong, believes that fewer people would use these products if they were more aware of the risks involved and the ingredients they contain.

"People like the idea of using a natural remedy because they think that if it is natural, it will be safe. There are two problems here. Firstly not all natural agents are harmless, and secondly the remedies also contain potentially harmful manufactured drugs," says Tang.

While the research concentrated on cases in Hong Kong, the work raises worldwide concerns. These slimming products are widely available over the counter not only in Hong Kong, but in other countries where drug regulation is relatively non-comprehensive. In addition, anyone can buy them over the Internet even if they live in regions with tighter regulatory control.

Doctors also need to ask patients about their use of over the counter slimming products if they come into a clinic with strange symptoms. "The active participation of front line medical staff together with toxicology laboratories is a crucial element in the long-term effort to eradicate this problem," says Tang.

Citation: Magdalene HY Tang, Sammy PL Chen, SW Ng, Albert YW Chan, Tony WL Mak, 'Case series on a diversity of illicit weight-reducing agents: from the well known to the unexpected', British Journal of Clinical Pharmacology, DOI: 10.1111/j.1365-2125.2010.03822.x